The present invention relates to a vehicle rear body structure of an automotive vehicle, particularly to the one that can properly improve absorption of an impact energy that acts on a vehicle rear body at a vehicle rear crash.
Generally, a vehicle rear body structure in which a pair of rear side frames is provided at both sides of the vehicle and a bumper beam extending in a vehicle width direction is attached to respective rear end portions of these rear side frames via respective crash cans operative to absorb an impact energy has been widely applied to automotive vehicles. When the vehicle has a rear crash, the crash cans are crashed with impact loads that are transmitted via the bumper beam and thereby the crash impact energy can be absorbed. The crash impact energy can be also absorbed by the rear side frames having their compressive deformations. Thus, the impact transmitted to a vehicle cabin can be absorbed properly at the vehicle rear crash.
Meanwhile, a structure in which a reinforcing member is provided at the vehicle rear body to increase a rigidity of the vehicle rear body is also known. For example, Japanese Patent Application Laid-Open No. 2004-322822 discloses a vehicle rear body structure, in which a pair of rear side lower frames, functioning as reinforcing members, is provided at respective lower end portions located outside a box-shape spare tire pan, and the rear side lower frames and the spare tire pan form a pair of closed cross sections that extends longitudinally substantially in parallel to a pair of rear side frames and is located at a lower level than the rear side frames.
The bumper beam is generally attached to the rear end portions of the rear side frames via the crash cans as described above. In the vehicle rear body structure disclosed in the above-described patent publication, however, the rear side lower frames (reinforcing members) are located at the lower end portion of the spare tire pan, namely, at a considerably lower level than the rear side frames. For this reason, it would be rather difficult to attach the bumper beam to the rear end portions of the rear side lower frames.
Herein, the bumper beam having a greater vertical width may be applied so that the bumper beam could be attached to both the rear side frames and the rear side lower frames. However, in this case, the bumper beam would be a rather large-sized and heavy beam and therefore the manufacturing costs would improperly increase.